Fact or Fiction?: Animals Like to Get Drunk

Stories abound about animals who have taken a nip—or 10. In 2004, Reuters reported that a black bear had passed out at the Baker Lake Resort in Washington State after binging on beer. Last October the Associated Press recounted a tale of six Indian elephants stumbling around and uprooting a utility pole, electrocuting themselves, after guzzling a homemade rice brew in the northeastern state of Meghalaya. Even Charles Darwin noted in The Descent of Man that monkeys have a “strong taste” for “spirituous liquors” and beer.

Still, there is scant scientific evidence proving that animals go on benders with the naturally occurring alcohol in fermenting fruit. Quite the contrary: the few studies done seemed to indicate they had either no interest or a distinct aversion to it. But new research, published in the Proceedings of the National Academy of Sciences, shows that at least a few creatures in the wilds of the Malaysian rainforest like to drink the hard stuff.

In the mid 1990s, Frank Wiens and Annette Ziztmann, animal physiologists at Germany’s University of Bayreuth, observed that tiny pentailed treeshrews frequent the bertam palm, returning regularly to nip the nectar. Wiens also noticed a strange yeasty aroma wafting from the plant, and what appeared to be foam like the head on a mug of beer.

“This indicated [to me] that there might be alcohol involved," Wiens recalls. He tested the nectar and, lo and behold, discovered that it was 3.8 percent alcohol, which is similar to that of some beers. Seems the bertam palm flower bud harbors a previously unknown species of yeast, which acts as a brewery, fermenting the nectar.

This botanic bartender knows how to please its customers: seven species of mammals in that west Malaysian rainforest, including the pentailed treeshrew and the slow loris, quaff alcohol nightly, sometimes going back for seconds and thirds in a single evening. In human terms, according to Wiens’ calculations, these diminutive creatures are regularly consuming the equivalent of about nine alcoholic beverages a night. Wiens says that it's a two-ways street: the animals get to enjoy a brew—or two or three—but they also act as the plant's pollinators.

Despite high alcohol levels, however, the furry little nippers didn’t get fuzzy—they displayed no overt signs of drunken behavior; there was no stumbling, swaying, passing out. Wiens speculates that the alcoholic nectar may still have some neurological effect in enticing them back for seconds, which, he says, makes sense from an evolutionary perspective. The animals get food, and the plant retains its pollinators.

Biologist Robert Dudley of the University of California Berkeley says this study is the first to demonstrate his theory that our attraction to alcohol evolved from a time when we roamed forests in search of energy-rich plants. A whiff of alcohol might have signaled that a fruit had reached peak calorie content. But like many adaptions that may once have been useful, he says, our evolutionary predilection for fermented fruit may lead to an unhealthy addiction to alcohol in today's world of plenty (just as we now just get fat instead of expending energy stored for use when food was scarce). And pentailed treeshrews are similar to the earliest pre-primates, a living model of extinct species from which shrews and primates, leading to humans, branched off.

“Humans have an affinity for ethanol (plant-derived alcohol), and captive primates are well known to like to drink anthropogenically sourced ethanol,” Dudley told Sciam.com. “Natural consumption of dietary ethanol deriving from fermenting fruits or nectar has never been studied previously, and this is a highly fruitful area for future investigation.”

The appeal of naturally occurring alcohol has not yet been investigated because, in the handful of previous studies, animals expressed no interest. Anthropologist Katherine Milton of UC Berkeley surveyed primate researchers, working with 22 species, on whether they had seen animals reach for fermented fruit. All said they had not. Scientists at Israel’s Ben Gurion University of the Negev studying bats reported that the animals shunned foods with elevated alcohol concentrations, despite higher sugar levels. Perhaps this is because, says animal physiologist Berry Pinshow, a co-author of that study, “a drunk bat is a dead bat.”

And the oft-heard tales of elephants getting sloshed off the fermented fruit of marula trees in South Africa’s Kruger National Park? Pure fiction. Physiologist Steve Morris of the University of Bristol in England calculates that, based on elephant size and metabolism, along with the alcohol content in fermenting marulas, an average elephant would have to eat more than 700 individual fruits to get looped .

But pentailed treeshrews—admittedly lightweights—prove that at least some animals enjoy a nightly cocktail.